Illumination device and image display apparatus

ABSTRACT

An illumination device includes: an excitation light source that emits excitation light having a first wavelength; and a fluorescent member that includes a fluorescent substance that, when it is irradiated with the excitation light, emits light having a second wavelength longer than the first wavelength, transmits a part of the excitation light and reflects another part of the excitation light, and a first reflective film provided at a side of the fluorescent substance, which is opposite to an excitation light incidence side, the fluorescent member emitting multiplexed light including an excitation light component reflected from the fluorescent substance and the first reflective film and a light component emitted from the fluorescent substance.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 14/334,014, filed Jul. 17, 2014 which is a continuation of U.S.patent application Ser. No. 13/155,468, filed Jun. 8, 2011 (U.S. Pat.No. 8,820,940), which claims priority from Japanese Patent ApplicationNo. JP 2010-139175 filed in the Japanese Patent Office on Jun. 18, 2010,the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to an illumination device and an image displayapparatus, and more particularly, to an illumination device used as alight source of a projection type image display apparatus such as aprojector, and an image display apparatus including the illuminationdevice.

Description of the Related Art

In recent years, in regard to watching movies at home, a presentation ata meeting, or the like, the opportunities to use a projection-type imagedisplay apparatus, such as a projector, have been increasing. In such aprojector, as a light source, for example, a discharge type lamp, suchas mercury lamp, having a high brightness is generally used. Inaddition, with the recent progress in the development techniques forsolid-state light emitting devices (for example, semiconductor lasers,light emitting diodes, or the like), there has been also suggested aprojector using the solid-state light emitting device (for example, seeJPA-2010-86815).

The projector disclosed in JP-A-2010-86815 is a DLP (Digital LightProcessing: registered trademark) type projector. In such a type ofprojector, images are displayed in full color through a time divisiondisplay of approximately several thousand times per second for thedifferent colors. Therefore, in the projector of JP-A-2010-86815, a redcolor light-emitting device, a green color light emitting device, and ablue color light emitting device those utilizing the solid-state lightemitting device are separately prepared, and emitted light from eachlight-emitting device is time-divisionally controlled, and is emitted tothe outside to display image light.

In addition, each of the light emitting devices, which are used in theprojector of JP-A-2010-86815, includes a light emitting wheel that isrotatably driven, a light emitting material that is formed on a surfaceof the light emitting wheel and absorbs excitation light and emits lightof a predetermined color, and an excitation light source (solid-statelight emitting device) that emits excitation light. In addition, as theexcitation light source used in each of the light emitting devices, alight source that emits excitation light with a wavelength band shorterthan that of light emitted from the light emitting material is used.

SUMMARY OF THE INVENTION

As described above, a projector not using a mercury lamp has beensuggested in the related art, and in such a projector, it is possible torealize a mercury-free projector in response to recent environmentproblems. In addition, in a case where for example, a solid-state lightemitting device such as a semiconductor laser and a light-emitting diodeis used as a light source, it has an advantage that durability is longerand a decrease in brightness is also lower compared to a mercury lamp.

However, the technique suggested in JP-A-2010-86815 is only applicableto a light source device (illumination device), for example, a DLP(registered trademark) type projector or the like that time-divisionallyemits plural kinds of single color light having wavelengths differingfrom each other. The technology suggested in JP-A-2010-86815 may be notapplicable to application where a light source device emitting whitelight is necessary, like an image display device such as a 3 LCD (LightCrystal Display) type projector or the like.

Thus, it is desirable to provide a mercury-free illumination device thatis also applicable to various applications such as a 3 LCD typeprojector and an image display apparatus having the illumination device.

An illumination device according to an embodiment of the inventionincludes an excitation light source that emits excitation light having afirst wavelength and a fluorescent member. The fluorescent memberincludes a fluorescent substance that, when it is irradiated with theexcitation light, emits light having a second wavelength longer than thefirst wavelength, transmits a part of the excitation light and reflectsanother part of the excitation light, and a first reflective filmprovided at a side of the fluorescent substance, which is opposite to anexcitation light incidence side. The fluorescent member emitsmultiplexed light including an excitation light component reflected fromthe fluorescent substance and the first reflective film, and a lightcomponent emitted from the fluorescent substance. In addition, theabove-described “wavelength” means a wavelength including not only asingle wavelength but also a predetermined wavelength band.

In addition, an image display apparatus according to another embodimentof the invention includes a light source device section and an imageprojection section, and a function of each section is as follows. Thelight source device section has substantially the same configuration asthat of the illumination device according to the embodiment of theinvention. The image projection section generates a predetermined imagelight by using the multiplexed light emitted from the light sourcedevice section and projects the generated image light to the outside.

According to the embodiment of the invention, the illumination device(light source device section) emits the multiplexed light including theexcitation light with a second wavelength that is emitted from thefluorescent substance and a part of the excitation light with a firstwavelength that is reflected from the fluorescent substance and thefirst reflective film. That is, according to the embodiment of theinvention, light having a wavelength band different from that of theexcitation light and the emission light is emitted. Therefore, accordingto the embodiment of the invention, in a case where the excitation lightis set as blue light and the emission light is set as light (forexample, yellow light or the like) including both red light and greenlight, it is possible to emit white light from the illumination device(light source device section).

As described above, in the illumination device (light source devicesection) according to the embodiment of the invention, it is possible toemit light having a wavelength band different from that of theexcitation light and the emission light, and by appropriately setting acombination of the first wavelength of the excitation light and thesecond wavelength of the emission light, it is possible to emit whitelight or the like. Therefore, according to the embodiment of theinvention, it is possible to provide a mercury-free illumination devicethat is also applicable to various applications such as a 3 LCD typeprojector and an image display apparatus having the illumination device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block configuration diagram illustrating an imagedisplay apparatus according to an embodiment of the invention;

FIGS. 2A to 2C are schematic configuration diagrams illustrating afluorescent member used for a light source device section (illuminationdevice);

FIG. 3 is a view illustrating a configuration example of a reflectivefilm used in a fluorescent member;

FIG. 4 is a view illustrating a spectral characteristic example of apolarization beam splitter used in a light source device sectionaccording to an embodiment of the invention;

FIG. 5 is a view illustrating an operation of the polarization beamsplitter;

FIG. 6 is a view illustrating a spectral characteristic of emitted lightof the light source device section (illumination device) according to anembodiment of the invention; and

FIG. 7 is a view illustrating a configuration example of a spectraloptical system according a modified example 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, description will be given to an example of an illuminationdevice and an image display apparatus having the same according to anembodiment of the invention with reference to accompanying drawings inthe following order. In addition, in this embodiment, a 3 LCD typeprojector is described as an example of the image display apparatus, butthe invention is not limited thereto. The invention may be applied toany image display apparatus where white light is necessary and the sameeffect may be obtained.

-   -   1. Configuration Example of Image Display Apparatus    -   2. Configuration Example of Light Source Device Section        (illumination device)    -   3. Configuration Example of Fluorescent Member    -   4. Configuration Example of Polarization Beam Splitter    -   5. Operation Example of Light Source Device Section    -   6. Various Modified Examples        [1. Configuration Example of Image Display Apparatus]

FIG. 1 shows a configuration example of an image display apparatusaccording to an embodiment of the invention. In FIG. 1, for simplicityof explanation, only main portions that are operated when image light isprojected to the outside in the image display apparatus 10 of thisembodiment are mainly shown. In addition, in FIG. 1, a configurationexample of a 3 LCD type projector is shown, but the invention is notlimited thereto. The invention may be applied to a 3 LCD type projectorusing a reflection-type LCD light modulation device.

The image display apparatus 10 includes a light source device section 1(illumination device) and an optical engine section 2 (image projectingsection). In addition, a configuration of the light source devicesection 1 will be described later.

The optical engine section 2 optically processes light (white light LWin this example) emitted from the light source device section 1 togenerate image light LI, and magnifies and projects the image light LIto, for example, an external screen. The optical engine section 2includes, for example, a spectral optical system 20, a 3 LCD opticalmodulation device (hereinafter, referred to as “a first LCD panel 21 tothird LCD panel 23”, respectively), a prism 24, and a projection opticalsystem 25. In addition, the configuration of the optical engine section2 is not limited to an example shown in FIG. 1 and may be appropriatelychanged, for example, according to usage or the like. For example,various necessary optical devices may be appropriately disposed on anoptical path between each of components inside the optical enginesection 2.

In addition, in the optical engine section 2 of this example, the firstand third LCD panels 21 and 23 are disposed with light emitting surfacesthereof opposed to each other, and the second LCD panel 22 is disposedin a direction orthogonal to an opposing direction of the first andthird LCD panels 21 and 23. The prism 24 is disposed at a regionencompassed by the first to third LCD panels 21 to 23. In addition, inthis example, the projection optical system 25 is disposed at a positionopposing a light emitting surface of the second LCD panel 22 with theprism 24 interposed therebetween. In addition, the spectral opticalsystem 20 is provided at a light incident side of the first to third LCDpanels 21 to 23.

The spectral optical system 20 is configured by, for example, a dichroicmirror, a reflective mirror or the like, disperses white light LWincident from the light source device section 1 into blue light LB,green light LG and red light LR and emits light of each wavelengthcomponent to each corresponding LCD panel. In this example, the spectraloptical system 20 emits each of the dispersed blue light LB, green lightLG and red light LR to the first LCD panel 21, the second LCD panel 22and the third LCD panel 23, respectively. In addition, in thisembodiment, in the spectral optical system 20, a polarization directionof each wavelength component is adjusted to be a predetermineddirection.

Each of the first to third LCD panels 21 to 23 is configured by atransmissive LCD panel. Each of the LCD panels transmits or shields(modulates) the incident light with a liquid crystal cell unit bychanging an arrangement of liquid crystal molecules enclosed in a liquidcrystal cell (not shown) on the basis of a driving signal supplied froma panel drive section (not shown). Each of the LCD panels emits themodulated light of a predetermined wavelength (modulated light) to theprism 24.

The prism 24 multiplexes the modulated light of each wavelengthcomponent incident from the first to third LCD panels 21 to 23,respectively, and emits the multiplexed light, that is, image light LIto the projection optical system 25.

The projection optical system 25 magnifies and projects the image lightincident from the prism 24 onto a display surface of, for example, anexternal screen or the like.

[2. Configuration Example of Light Source Device Section 1]

Next, an internal configuration of the light source device section 1 ofthis embodiment will be described with reference to FIG. 1. The lightsource device section 1 includes an excitation light source 11, apolarization beam splitter 12 (a spectral optical system), a quarterwavelength plate 13, a condensing optical system 14 (optical system), afluorescent member 15, and a motor 16 (driving unit).

In the light source device section 1 of this embodiment, a reflectivefilm 31 and a fluorescent layer 32, which are described later, of thefluorescent member 15, the condensing optical system 14, the quarterwavelength plate 13 and the polarization beam splitter 12 are disposedon an optical path of emitted light from the fluorescent member 15 inthis order from the fluorescent member 15 side. In addition, theexcitation light source 11 is disposed in a direction orthogonal to theoptical path of the emitted light from fluorescent member 15 and at alocation opposing one light incident surface of the polarization beamsplitter 12.

The excitation light source 11 is configured by a solid-state lightemitting device that emits light of a predetermined wavelength (a firstwavelength). In this example, as the excitation light source 11, a bluelaser emitting blue light (excitation light Bs) with a wavelength of 445nm is used. In addition, excitation light Bs of linear polarizationlight (S polarization light) is emitted from the excitation light source11. In addition, in this embodiment, a wavelength of the excitationlight is set to a wavelength shorter than that of light (hereinafter,referred to as “emission light”) emitted from the fluorescent layer 32that is described later, in the fluorescent member 15.

In addition, in a case where the excitation light source 11 isconfigured by a blue laser, it may be configured to obtain excitationlight Bs with a predetermined output by one blue laser, and it may beconfigured to multiplex emitted light from each of plural blue lasersand obtain excitation light Bs with a predetermined output. In addition,a wavelength of the blue light (excitation light Bs) is not limited to445 nm, and it is possible to use any wavelength as long as thewavelength is within a wavelength band of light called blue light.

The polarization beam splitter 12 (PBS) separates excitation light Bsincident from the excitation light source and emitted light (multiplexedlight) incident from the fluorescent member 15. Specifically, thepolarization beam splitter 12 reflects the excitation light Bs incidentfrom the excitation light source 11 and emits the reflected light to thefluorescent member 15 via the condensing optical system 14. In addition,the polarization beam splitter 12 transmits light emitted from thefluorescent member 15 and emits the transmitted light to the spectraloptical system 20 in the optical engine section 2.

In this embodiment, a spectral characteristic of the polarization beamsplitter 12 is designed to realize the above-described light separatingoperation in the polarization beam splitter 12. In addition, a specificexample of the spectral characteristic of the polarization beam splitter12 will be described later. In addition, as a configuration of anoptical system that separates the excitation light Bs incident from theexcitation light source 11 and the emitted light from the fluorescentmember 15, it is not limited to the polarization beam splitter 12 andany optical system may be used as long as it is configured to performthe above-described light separating operation.

The quarter wavelength plate 13 is a phase element that generates aphase difference of π/2 with respect to the incident light. In a casewhere the incident light is linearly polarized light, the quarterwavelength plate 13 converts the linearly polarized light to circularlypolarized light. In a case where the incident light is circularlypolarized light, the quarter wavelength plate 13 converts the circularlypolarized light to linearly polarized light. In this embodiment, thequarter wavelength plate 13 converts a linearly polarized excitationlight emitted from the polarization beam splitter 12 to circularlypolarized excitation light and converts a circularly polarizedexcitation light component included in the multiplexed light emittedfrom the fluorescent member 15 to linearly polarized light.

The condensing optical system 14 condenses the excitation light emittedfrom the quarter wavelength plate 13 to have a predetermined spotdiameter, and emits the condensed excitation light (hereinafter,referred to as “condensed light”) to the fluorescent member 15. Inaddition, the condensing optical system 14 converts the multiplexedlight emitted from the fluorescent member 15 into parallel light andemits the parallel light to the quarter wavelength plate 13. Inaddition, the condensing optical system 14 may be configured by, forexample, a single collimator lens or may be configured to convertincident light into parallel light by using plural lenses.

The fluorescent member 15 absorbs a part of the excitation light (bluelight) incident through the condensing optical system 14, emits lightwith a predetermined wavelength band (a second wavelength) and reflectsthe remainder of the excitation light. The fluorescent member 15multiplexes the emission light and a part of the excitation light thatis reflected and emits the multiplexed light to the condensing opticalsystem 14.

In this example, since light incident to the optical engine section 2 isset as white light LW, the fluorescent member 15 emits light in awavelength band (approximately 480 to 680 nm) including red light andgreen light. In this embodiment, the emission light in a wavelength bandincluding red light and green light and a part of the excitation light(blue light) that is reflected by the fluorescent member 15 (areflective film 31 and a fluorescent layer 32 that are described later)are multiplexed and white light is generated. In addition, a moredetailed configuration of the fluorescent member 15 will be describedlater.

In addition, since the emission light emitted from the fluorescentmember 15 is light that expands in a Lambertian (uniform diffusion)shape, when the distance between the condensing optical system 14 andthe fluorescent member 15 is long, it is difficult to sufficientlycondense the emission light through the condensing optical system 14,and thereby usage efficiency of excitation light decreases. In addition,when the spot diameter of the excitation light emitted to thefluorescent member 15 is oversized, expansion of the emission lightbecomes larger and thereby the usage efficiency decreases. Therefore, inthis embodiment, the configuration of the condensing optical system 14such as lens configuration, focal point distance and alignment position,and the distance between the condensing optical system 14 and thefluorescent member 15 are set so as to obtain sufficient usageefficiency of excitation light.

The motor 16 rotatably drives the fluorescent member 15 for apredetermined number of rotations. At this time, the motor 16 drives thefluorescent member 15 so that the fluorescent member 15 rotates in aplane (an irradiation plane of the excitation light of the fluorescentlayer 32) orthogonal to the irradiation direction of the excitationlight. Due to this, the irradiation position of the excitation light inthe fluorescent member 15 varies (moves) with the passage of time at aspeed corresponding to the number of rotations in a plane orthogonal tothe irradiation direction of the excitation light.

As described above, the fluorescent member 15 is rotatably driven by themotor 16 and the irradiation position of the excitation light in thefluorescent member 15 varies with the passage of time, such that it ispossible to suppress an increase in the temperature at the irradiationposition and it is possible to prevent the light emission efficiency ofthe fluorescent layer 32 from being decreased. In addition, it takessome (for example, several nsec) for fluorescent atoms to absorb theexcitation light and to emit light, and even when the next excitationlight is emitted to the fluorescent atoms for the excitation period, theatoms do not emit light. However, according to this embodiment, theirradiation position of the excitation light in the fluorescent member15 varies with the passage of time, such that the fluorescent atoms notexcited are sequentially disposed at the irradiation position of theexcitation light and thereby it is possible to allow the fluorescentlayer 32 to efficiently emit light.

In addition, in this embodiment, an example where the fluorescent member15 is rotatably driven by the motor 16 is illustrated. However, theinvention is not limited thereto and may be configured in any manner aslong as the irradiation position of the excitation light in thefluorescent member 15 varies with the passage of time. For example, theirradiation position of the excitation light may vary with the passageof time by making the fluorescent member 15 lineally reciprocate in apredetermined direction in a plane orthogonal to the irradiationdirection of the excitation light. In addition, the irradiation positionof the excitation light may vary with the passage of time by fixing thefluorescent member 15 and by relatively moving the excitation lightsource 11 and various optical systems with respect to the fluorescentmember 15.

[3. Configuration Example of Fluorescent Member]

Next, a detailed configuration of the fluorescent member 15 will bedescribed with reference to FIGS. 2A to 2C. In addition, FIG. 2A shows afront view of the fluorescent member 15 seen from the condensing opticalsystem 14 side, FIG. 2B shows a cross sectional view taken along a lineA-A of FIG. 2A, and FIG. 2C shows a front view of the fluorescent member15 seen from a side opposite to the condensing optical system 14.

The fluorescent member 15 includes a disk-shaped substrate 30, areflective film 31 (a first reflective film) formed on one surface(incidence side of excitation light) of the substrate 30 and thefluorescent layer 32 (fluorescent substance).

The substrate 30 is formed from a transparent material such as glass andtransparent resin. In addition, the material for forming the substrate30 is not limited to a transparent material and may be formed from anymaterial as long as the material has a predetermined strength. Inaddition, a size such as the thickness of the substrate 30 isappropriately set in consideration of the necessary strength, weight orthe like. In addition, the center of the substrate 30 is attached to arotational shaft 16 a of the motor 16 and the substrate 30 is fixed tothe rotational shaft 16 a by a fixing hub 16 b.

As shown in FIG. 2A, the reflective film 31 is formed on one surface ofthe substrate 30 with a doughnut shape. The doughnut-shaped reflectivefilm 31 is disposed on the substrate 30 in a manner such that thereflective film 31 and the substrate 30 are concentric to each other. Inaddition, a width of the reflective film 31 in the radial directionthereof is set to a value larger than the spot size of the excitationlight (condensed light) condensed by the condensing optical system 14.

The reflective film 31 reflects the entire light regardless of awavelength and an incidence angle of incident light. Therefore, thereflective film 31 not only reflects the light (emission light) excitedat the fluorescent layer 32 to the condensing optical system 14 side,but also reflects a part of the excitation light (blue light)transmitted through the fluorescent layer 32 to the condensing opticalsystem 14 side.

Here, FIG. 3 shows one configuration example of the reflective film 31.The reflective film 31 is formed by alternately laminating a firstdielectric layer 31 a formed from, for example, a SiO2 layer, a MgF2layer or the like and a second dielectric layer 31 b formed from, forexample, a TiO2 layer, a Ta2O3 layer or the like on the substrate 30.Specifically, the reflective film 31 may be configured by a dichroicmirror (dichroic film). In a case where the reflective film 31 isconfigured by a dichroic mirror as shown in FIG. 3, by the adjustment ofa lamination count of each dielectric layer, the thickness of eachdielectric layer, a forming material of each dielectric layer, or thelike, it is possible to set a reflective (transmissive) characteristicof the reflective layer 31 to a predetermined characteristic. Inaddition, the lamination count of each of the first dielectric layer 31a and the second dielectric layer 31 b may generally be several layersto several tens of layers. In addition, the first dielectric layer 31 aand the second dielectric layer 31 b are formed by, for example, avapor-deposition method, a sputtering method or the like. In addition,the configuration of the reflective film 31 is not limited to theexample shown in FIG. 3, and may be formed from, for example, a metalfilm such as aluminum.

The fluorescent layer 32 may be formed from a layer-shaped fluorescentsubstance, and absorbs a part of the excitation light and emits lightwith a predetermined wavelength when the excitation light is incidentthereto. In addition, the fluorescent layer 32 transmits a part of theremaining excitation light that is not absorbed and diffuses (reflects)the remainder thereof. In addition, an excitation light componentreflected from the fluorescent layer 32 becomes non-polarized light.

In this embodiment, a part of the excitation reflected from thereflective film 31 and the fluorescent layer 32 and the emission lightat the fluorescent layer 32 are multiplexed and white light isgenerated, such that the fluorescent layer 32 may be formed from, forexample, a YAG (Yttrium Aluminum Garnet)-based fluorescent material orthe like. In this case, the fluorescent layer 32 emits light (yellowlight) with a wavelength band of 480 to 680 nm when blue excitationlight is incident thereto.

In addition, as the fluorescent layer 32, a film of any configurationand material may be used as long as the film can emit light with awavelength band including blue light and green light, and it ispreferable that a film formed from a YAG-based fluorescent material isused, from the view point of light-emitting efficiency and heatresistance.

The fluorescent layer 32 is formed by applying a predeterminedfluorescent agent obtained by mixing a fluorescent material and a binderon the reflective film 31. In the example shown in FIGS. 2A to 2C, thefluorescent layer is formed so as to cover the entire surface of thereflective film 31, such that the surface shape of the fluorescent layer32 become a doughnut shape. In addition, the fluorescent layer 32 may beformed only at a region where the excitation light is emitted thereto,such that the shape of the fluorescent layer 32 is not limited to theexample shown in FIGS. 2A to 2C, and a width of the fluorescent layer ina radial direction may be narrower than that of the reflective film 31.

In addition, in regard to the fluorescent layer 32, the light emissionamount, and the ratio of the transmission amount to the reflectionamount (diffusion amount) of the excitation light may be adjusted by thethickness of the fluorescent layer 32, the density (contained amount) ofthe fluorescent substance, or the like. Therefore, in this embodiment,the thickness of the fluorescent layer 32, the density of thefluorescent substance, or the like is adjusted so that the emitted lightfrom the light source device section 1 becomes white light.

In addition, in the fluorescent member 15 of the above-describedembodiment, an example where the layer-shaped fluorescent substance(fluorescent layer 32) is formed on the substrate 30 via the reflectivefilm 31 is described, but the invention is not limited thereto. Forexample, in a case where the fluorescent substance is configured by aplate-shaped member having a sufficient strength, the substrate 30 maybe not provided. In addition, in this case, the reflective film 31 maybe directly formed on one surface of the fluorescent substance formedfrom a plate-shaped member, or a reflective mirror is preparedseparately from the fluorescent substance and the reflective mirror maybe used instead of the reflective film 31.

[4. Configuration of Polarization Beam Splitter]

In the light source device section 1 of this embodiment, as shown inFIG. 1, an optical path of the excitation light incident to thefluorescent member 15 from the excitation light source 11 via thepolarization beam splitter 12, and an optical path of the multiplexedlight incident to the optical engine section 2 from the fluorescentmember 15 are overlapped with each other. Therefore, in this embodiment,as described above, a spectral characteristic of the polarization beamsplitter 12 is appropriately adjusted to separate both light beams.

FIG. 4 shows a view illustrating a spectral characteristic example ofthe polarization beam splitter 12 used in this embodiment. In addition,in the spectral characteristic shown in FIG. 4, a horizontal axisrepresents a wavelength, and a vertical axis represents a transmittance.In addition, a characteristic Tp depicted by a solid line in FIG. 4represents a transmittance characteristic of the polarization beamsplitter 12 with respect to P-polarized incident light, and acharacteristic Rp depicted by a broken line represents a reflectancecharacteristic of the polarization beam splitter 12 with respect toP-polarized incident light. In addition, a characteristic Ts depicted bydotted line in FIG. 4 represents a transmittance characteristic of thepolarization beam splitter 12 with respect to S-polarized incidentlight, and a characteristic Rs depicted by one-dotted line represents areflectance characteristic of the polarization beam splitter 12 withrespect to S-polarized incident light.

In the polarization beam splitter 12 used in this embodiment, as shownin FIG. 4, in regard to an optical component with a wavelength band of480 to 680 nm that is emitted from the fluorescent layer 32, thetransmittance is approximately 100% and the reflectance is approximately0%, regardless of a polarization direction. That is, all of the light(yellow light) with a wavelength band of 480 to 680 nm is transmittedthrough the polarization beam splitter 12.

On the other hand, as shown in FIG. 4, the transmittance of thepolarization beam splitter 12 with respect to the P-polarized blue lightis approximately 100% and the reflectance is approximately 0%. Inaddition, the transmittance of the polarization beam splitter 12 withrespect to the S-polarized blue light is approximately 0% and thereflectance is approximately 100%. That is, the polarization beamsplitter 12 transmits light when P-polarized blue light is incidentthereto, and reflects light when S-polarized blue light is incidentthereto.

By setting the spectral characteristics of the polarization beamsplitter 12 to the characteristics shown in FIG. 4, the excitation lightincident to the fluorescent member 15 and the emitted light from thefluorescent member 15 can be separated from each other. Specifically,the excitation light Bs (blue light) incident from the excitation lightsource 11 is S-polarized light, such that it is reflected by thepolarization beam splitter 12 and is guided to the fluorescent member15.

On the other hand, the emission light component included in themultiplexed light emitted from the fluorescent member 15 is an opticalcomponent with a wavelength band of 480 to 680 nm, such that it istransmitted through the polarization beam splitter 12. In addition, inthe excitation light (blue light) components included in the multiplexedlight emitted from the fluorescent member 15, the excitation lightcomponent reflected from the reflective film 31 is P-polarized light asdescribed below, such that it is transmitted through the polarizationbeam splitter 12. In addition, in the excitation light componentsincluded in the multiplexed light emitted from the fluorescent member15, the excitation light component directly reflected from fluorescentlayer 32 is non-polarized light, such that approximately half of theexcitation light component is transmitted through the polarization beamsplitter 12. That is, a part of the multiplexed light emitted from thefluorescent member 15 is transmitted through polarization beam splitter12 and the transmitted multiplexed light is guided as white light LW tothe spectral optical system 20 in the optical engine section 2.

[5. Operation Example of Light Source Device Section]

Next, an operation example of a light source device section of thisembodiment will be described in detail with reference to FIGS. 1 to 5.In addition, FIG. 5 shows a view illustrating a state of an operation ofthe polarization beam splitter 12 of this embodiment. In FIG. 5, thecircle A1 represents an S-polarization direction and the white arrow A2represents a P-polarization direction. In addition, in FIG. 5, forsimplicity of description, a non-polarized excitation light componentdirectly reflected from the fluorescent layer 32 is not shown.

First, the excitation light source 11 emits S-polarized excitation lightBs (blue light) to the polarization beam splitter 12. Subsequently, thepolarization beam splitter 12 reflects the incident excitation light Bsin a direction facing the fluorescent member 15. Subsequently, thepolarization beam splitter 12 emits the reflected excitation light tothe condensing optical system 14 via the quarter wavelength plate 13.Subsequently, the condensing optical system 14 condenses the incidentexcitation light to have a predetermined spot diameter and emits thecondensed light to the fluorescent member 15.

Subsequently, when the excitation light is emitted to the fluorescentlayer 32 of the fluorescent member 15, the fluorescent layer 32 absorbsa part of the excited light and thereby emits light (yellow light) witha wavelength band of 480 to 680 nm including red light and green light.In addition, at this time, the fluorescent layer 32 diffuses a part ofthe excitation light that is not absorbed at the fluorescent layer 32side and reflects it to the condensing optical system 14 side, andtransmits a part of the remaining excitation light that is not absorbedand guides it the reflective film 31. The reflective film 31 reflectsthe excitation light that is transmitted through the fluorescent layer32 to the condensing optical system 14 side. In addition, at this time,a part of the emission light of the fluorescent layer 32 is reflectedfrom the reflective film 31 to the condensing optical system 14 side.

As a result, the emission light from the fluorescent layer 32 and a partof the excitation light reflected from the fluorescent layer 32 andreflective film 31 are multiplexed in the fluorescent member 15, and themultiplexed light is emitted from the fluorescent member 15 to thecondensing optical system 14.

Subsequently, the condensing optical system 14 converts the multiplexedlight emitted from the fluorescent member 15 into parallel light andemits the parallel light to the polarization beam splitter 12 via thequarter wavelength plate 13.

At this time, a light component included in the multiplexed light thatpasses through the quarter wavelength plate 13, that is, a red lightcomponent Rps (broken line arrow in FIG. 5) and a green light componentGps (one-dotted line arrow) are non-polarized light (including aP-polarized component and a S-Polarized light component). Therefore, thered light component Rps and green light component Gps included in themultiplexed light transmit through the quarter wavelength plate 13 “asis” and are incident to the polarization beam splitter 12.

On the other hand, in the excitation light component (blue lightcomponent) included in the multiplexed light, the excitation lightcomponent reflected from the reflective film 31 passes through thequarter wavelength plate 13 a total of two times until it is incident tothe polarization beam splitter 12. Specifically, the excitation lightcomponent reflected from the reflective film 31 passes through,respectively, the quarter wavelength plate 13 in an optical path fromthe excitation light source 11 to the fluorescent member 15 and theoptical path from the fluorescent member 15 to the polarization beamsplitter 12 one at a time. Therefore, a polarization direction of thereflected light component from the reflective film 31, which is includedin the multiplexed light after passing through the quarter wavelengthplate 13, is rotated by 90° with respect to the excitation light Bsemitted from the excitation light source 11.

In this embodiment, the excitation light Bs emitted from the excitationlight source 11 is S-polarized light, such that the excitation lightcomponent Bp (blue light) incident to the polarization beam splitter 12after being reflected from the reflective film 31 becomes P-polarizedlight as shown in FIG. 5. On the other hand, since the excitation lightcomponent (not shown in FIG. 5) directly reflected from the fluorescentlayer 32 is non-polarized light, it passes through the quarterwavelength plate 13 “as is”, and is incident to the polarization beamsplitter 12 (not shown in FIG. 5).

In addition, in this embodiment, the polarization beam splitter 12 ismade to have a spectral characteristic as shown in FIG. 4, such that thepolarization beam splitter 12 passes the red light component Rps and thegreen light component Gps included in the multiplexed light “as is”.

In addition, in the excitation light components incident to thepolarization beam splitter 12, the reflected light component (Bp) fromthe reflective film 31 is P-polarized light, such that the polarizationbeam splitter 12 passes the reflected light component (Bp) from thereflective film 31 “as is”. Therefore, in the excitation lightcomponents incident to the polarization beam splitter 12, the reflectedlight component from the fluorescent layer 32 is non-polarized light,such that the polarization beam splitter 12 passes only the P-polarizedlight in the reflected light components. At this time, in the excitationlight components reflected from the fluorescent layer 32, the ratio ofcomponent passing through the polarization beam splitter 12 isapproximately 50%. Therefore, in this embodiment, in the excitationlight component emitted from the fluorescent member 15, an excitationlight component of approximately 70 to 80% passes through thepolarization beam splitter 12.

As a result, light obtained by multiplexing the red light component Rps,the green light component Gps, and a part of excitation light component(blue light component) reflected from the reflective film 31 and thefluorescent layer 32, that is, white light LW is emitted from a lightemitting surface, which is located at the optical engine section 2 side,of the polarization beam splitter 12. In this embodiment, the whitelight LW is emitted from the light source device section 1 as describedabove.

In regard to the light source device section 1 having theabove-described configuration of this embodiment, the present inventorset parameters of each portion of the light source device section 1 asdescribed below and examined spectral characteristics of emitted lightfrom the light source device section 1.

-   -   Wavelength of the excitation light source 11 (blue laser): 445        nm    -   Condensing diameter of excitation light: 1 mm    -   Incidence angle θ of excitation light: 20° or less    -   Spectral characteristics of the polarization beam splitter 12: a        characteristic shown in FIG. 4    -   Distance between the condensing optical system 14 and the        fluorescent layer 32: 1 mm or less    -   Number of rotations of the fluorescent member 15: 3000 rpm    -   Forming material of the fluorescent layer 32: A YAG-based        fluorescent substance    -   Thickness of the fluorescent layer 32: 50 μm    -   Width of the fluorescent layer 32: 5 mm

FIG. 6 shows a spectral characteristic of an emitted light from thelight source device section 1, which is obtained under theabove-described condition. In addition, in the characteristic shown inFIG. 6, a horizontal axis represents a wavelength, and a vertical axisrepresents intensity (any unit) of the emitted light. As can be seenfrom FIG. 6, under the conditions, it can be seen that a light component(blue light component) near a wavelength of 445 nm and a light componentwith a wavelength ranging from approximately 480 to 680 nm, that is, alight component including a red light component and a green lightcomponent are included in the emitted light. From this, it can be seenthat white light is emitted from the light source device section 1 ofthis embodiment.

As described above, it is possible to emit the white light from lightsource device section 1 by using a solid-state light emitting device.Therefore, this embodiment may be applied for application where a lightsource device emitting white light is necessary, for example, like in a3 LCD type projector. That is, in this embodiment, it is possible toprovide a mercury-free light source device section 1 (illuminationdevice), which can be applied for various applications, and an imagedisplay apparatus 10 having the same.

In the light source device section 1 of this embodiment, it is notnecessary to use a mercury lamp, such that it is possible to cope with arecent environmental problem. In addition, according to this embodiment,it is possible to provide a light source device section 1 of whichdurability is longer and decrease in brightness is also lower comparedto the mercury lamp, and an image display apparatus 10. In addition,like in this embodiment, when a solid-state light emitting device isused in the excitation light source device section 11, a lighting timemay be shortened compared to the mercury lamp.

In addition, in a case where a semiconductor laser is used as theexcitation light source 11 like in the light source device section 1 ofthis embodiment, light with a sufficiently high brightness may beemitted compared to a solid-state light source such as an LED (LightEmitting Diode) and thereby it is possible to realize a high brightnesslight source. In addition, like in this embodiment, a configurationwhere the fluorescent layer 32 is made to emit light by using a bluelight laser to generate white light is simpler and cheaper than aconfiguration where solid-state light sources for red light, greenlight, and blue light are separately prepared to generate white light.

[6. Various Modified Examples]

(1) MODIFIED EXAMPLE 1

In this embodiment, there is described an example where excitation lightincident to the fluorescent member 15 and white light are separated byusing the polarization beam splitter 12, but the invention is notlimited thereto. For example, a reflective mirror, which is configuredto reflect blue light at some regions, may be used instead of thepolarization beam splitter 12. An example thereof (modified example 1)is shown in FIG. 7.

A reflective mirror 40 (spectral optical system) of modified example 1includes a plate-shaped transparent substrate 41 (base) and a reflectivefilm 42 (second reflective film) that is formed one surface of thetransparent substrate 41. The reflective film 42 is formed with a sizeapproximately equal to the spot diameter of excitation light. Inaddition, in this example, the reflective film 42 is disposed at anirradiation position of the excitation light and the reflective mirror40 is disposed inside of the light source device section 1 in a mannerthat a surface of the reflective mirror 40 is slanted approximately 45°with respect to an incidence direction of excitation light.

The transparent substrate 41 is formed from, for example, a glass or atransparent material such as a transparent resin, and the reflectivefilm 42 may be configured by, for example, a dichroic mirror (dichroicfilm) shown in FIG. 3. In a case where the reflective film 42 isconfigured by the dichroic mirror, by adjusting a forming material ofeach dielectric layer and a thickness of the dielectric layer and alamination count, or the like, it is possible to selectively reflectblue light and transmit another wavelength component. In addition, thereflective film 42 may be formed from a metal film such as aluminum.

In a case where the reflective mirror 40 having a configuration shown inFIG. 7 is used, excitation light from the excitation light source 11 isreflected from the reflective film 42 and is incident to the fluorescentmember 15. On the other hand, multiplexed light (white light LW), whichis incident to the reflective mirror 40 from the fluorescent member 15via condensing optical system 14, mainly passes through a region wherethe reflective film 42 is not formed and is incident to the opticalengine section 2. In addition, in a case where the reflective film 42 isdesigned to transmit light with a wavelength band other than blue light,red light component and green light component included in themultiplexed light (white light LW) also pass through the region wherethe reflective film 42 is formed.

In this example, in a case where a semiconductor laser is used as theexcitation light source 11, the spot diameter of excitation lightemitted from the excitation light source 11 is sufficiently smaller thanthat of each multiplexed light (white light LW) emitted from thecondensing optical system 14. Therefore, it is also possible to emitwhite light LW with a sufficiently large strength from the light sourcedevice section 1 in the configuration of this example.

In addition, like in this example, in a case where the reflective mirror40 is used as a spectral optical system for separating the excitationlight incident to the fluorescent member 15 and the multiplexed lightincident to the optical engine section 2, it is possible to make theconfiguration of the spectral optical system simpler. In theconfiguration of this example, since it is not necessary to consider apolarization direction of light incident to reflective mirror 40, it isnot necessary to provide the quarter wavelength plate 13 like in theembodiment. Therefore, in this example, it is possible to make theconfiguration of the light source device section 1 simple and it ispossible to provide a cheap light source device section 1.

(2) MODIFIED EXAMPLE 2

In the embodiment and modified example 1, there is described an examplewhere the spectral optical system (polarization beam splitter 12 orreflective mirror 40) reflects the excitation light emitted from theexcitation light source 11 and transmits the multiplexed light emittedfrom the fluorescent member 15. However, the invention is not limitedthereto.

For example, the spectral optical system may be configured to transmitthe excitation light emitted from the excitation light source 11, guideit the fluorescent member 15, reflect the multiplexed light emitted fromthe fluorescent member 15 and guide it the optical engine section 2. Inaddition, in this case, the excitation light incident to thepolarization beam splitter 12 from the excitation light source 11 is setas P-polarized light.

(3) MODIFIED EXAMPLE 3

In the embodiment, there is described an example where the quarterwavelength plate 13 is provided in the light source device section 1,but the invention is not limited thereto. For example, in a usage wherewhite light with a high output is not necessary, the quarter wavelengthplate 13 may be not provided.

In a case where the quarter wavelength plate 13 is not provided, theS-polarized excitation light is directly incident to the fluorescentlayer 32 via the polarization beam splitter 12 and the condensingoptical system 14. In this case, a part of the excitation light incidentto the fluorescent layer 32 diffuses in the fluorescent layer 32 and anon-polarized excitation light component is reflected to the condensingoptical system 14. In the excitation light components reflected from thefluorescent layer 32, only P-polarized light component is transmittedthrough the polarization beam splitter 12. In addition, the excitationlight component reflected from the reflective film 31 is S-polarizedlight, the excitation light component does not transmit through thepolarization beam splitter 12. Therefore, in the configuration of thisexample, white light including the P-polarized light component of theexcitation light reflected from the fluorescent layer 32 and emissionlight from the fluorescent layer 32 is emitted from the light sourcedevice section 1.

In addition, in the configuration of this example, the excitation lightcomponent included in the white light (multiplexed light) emitted fromthe light source device section 1 includes only the P-polarized lightcomponent reflected from the fluorescent layer 32. Therefore, in thisexample, the intensity of the emitted light and the usage efficiency ofexcitation light decrease compared to the embodiment. However, in thelight source device section 1 of this example, it is not necessary toprovide the quarter wavelength plate 13, such that the configurationthereof becomes relatively simple compared to the embodiment.

(4) MODIFIED EXAMPLE 4

In the embodiment and the modified example 1, there is described anexample where the excitation light incident to the fluorescent member 15and the multiplexed light emitted from the fluorescent member 15 areseparated by using the spectral optical system (the polarization beamsplitter 12 or the reflective mirror 40), but the invention is notlimited thereto. For example, in a case where the excitation light isincident obliquely with respect to the fluorescent member 15 and themultiplexed light emitted from the fluorescent member 15 is condensed inan optical path different from that of the excitation light, theabove-described spectral optical system and quarter wavelength plate 13may be not provided. In this case, the configuration of the light sourcedevice section 1 becomes relatively simple.

(5) MODIFIED EXAMPLE 5

In the embodiment, there is described an example where the condensingoptical system 14 is provided in the light source device section 1, butthe invention is not limited thereto. For example, in a case where thelight source device section 1 of the embodiment is applied for a usagewhere white light with a high output is not necessary, the light sourcedevice section 1 may be configured so as not to include the condensingoptical system 14.

(6) MODIFIED EXAMPLE 6

In the embodiment, there is described an example where the emitted lightof the light source device section 1 (illumination device) is set aswhite light, but the invention is not limited thereto. For example, asthe emitted light, blue light may be used for a usage where cyan light(or magenta light) is necessary as the excitation light, or thefluorescent layer 32 may be formed by a fluorescent material that emitsonly green light (or red light). That is, according to a necessarywavelength (color) of the emitted light, a combination of the wavelengthof the excitation light and the material for forming the fluorescentlayer 32 may be appropriately selected. In this case, an applicableusage range may be more extendable.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. An illumination device comprising: an excitationlight source configured to emit excitation light having a firstwavelength range; and a single rotating fluorescent portion configuredto include a fluorescent substance that, responsive to being irradiatedwith the excitation light, emits emission light having a secondwavelength range which is different from the first wavelength range, anda reflective portion that is provided at a side of the fluorescentsubstance, which is opposite to an excitation light incidence side, andreflects the emission light emitted from the fluorescent substance,wherein the fluorescent substance is provided continuously along anentirety of a circumference of the reflective portion.
 2. Theillumination device of claim 1, wherein the first wavelength range is inat least a blue spectrum and the second wavelength range is in at leasta red spectrum and a green spectrum.
 3. The illumination deviceaccording to claim 1, further comprising a driving unit configured tochange an irradiation position of the excitation light in the singlerotating fluorescent portion with passage of time.
 4. The illuminationdevice according to claim 1, wherein the reflective portion comprises areflective film which reflects the excitation light and guides theexcitation light to the fluorescent substance.
 5. The illuminationdevice according to claim 1, further comprising: a spectral opticalsystem that is provided at the excitation light incidence side of thefluorescent substance, configured to receive the excitation lightemitted from the excitation light source and the emission light emittedfrom the fluorescent substance, and separate the incident excitationlight and the emission light emitted from the fluorescent substance. 6.The illumination device according to claim 5, wherein the excitationlight is linearly polarized light, and the spectral optical systemincludes a polarization beam splitter.
 7. The illumination deviceaccording to claim 6, further comprising: a quarter wavelength plateprovided between the polarization beam splitter and the single rotatingfluorescent portion.
 8. The illumination device according to claim 1,further comprising: an optical system configured to convert the emissionlight from the fluorescent substance into parallel light.
 9. Theillumination device according to claim 1, wherein the excitation lightincludes a blue light having at least a wavelength of 445 nm and thesecond wavelength range includes at least a wavelength band of 480 to680 nm.
 10. The illumination device according to claim 1, wherein thefluorescent substance is formed only from Yttrium Aluminum Garnet-basedfluorescent material.
 11. The illumination device according to claim 1,wherein the fluorescent substance is formed continuously along acircumferential direction.
 12. The illumination device according toclaim 1, wherein a shape of the fluorescent substance is a doughnutshape.
 13. The illumination device according to claim 1, wherein thefluorescent substance is formed from a single fluorescent material. 14.An image display apparatus comprising: a light source device section;and an image projection section configured to generate a predeterminedimage light by using light emitted from the light source device sectionand project the generated image light to the outside, wherein the lightsource device section includes: an excitation light source configured toemit excitation light having a first wavelength range, and a singlerotating fluorescent portion configured to include a fluorescentsubstance that, responsive to being irradiated with the excitationlight, emits emission light having a second wavelength range which isdifferent from the first wavelength range, and a reflective portion thatis provided at a side of the fluorescent substance, which is opposite toan excitation light incidence side, and reflects the emission lightemitted from the fluorescent substance, wherein the fluorescentsubstance is provided continuously along an entirety of a circumferenceof the reflective portion.